FIA banned it too early, no fun.
It was used to be fun to see teams trying to catch up with innovative technology every season, such as F-Duct, Double Deck Diffusor, Blown Diffusor, Flex-Front Wing, etc etc.

A few years ago, it seemed like new tech wouldn't get banned until after it had run a race. I would like to see this become a rule so as to not instantly bin possibly months of hard work.